1. Field of the Invention
This invention relates generally to the labeling of X-ray film and, more particularly, to providing identification data in the permanent emulsion of X-ray images.
2. Description of the Related Art
When X-ray images are taken, such as for viewing anatomical structures, they must be labeled with data to identify the patient and the viewing orientation. For example, the patient's name and the side of the body being viewed are exposed into the X-ray film emulsion layer, leaving the information permanently part of the X-ray image. There are two major types of conventional X-ray labeling methods. The first method is to use a lead strip or lead formed letters to provide identification data in an exposed X-ray image as the image is created. In the case of a lead strip, the identification data is embossed into the strip and creates a mask or stencil that is placed over the X-ray film. In the case of lead formed letters, groups of letters must be assembled into the desired information and placed over the X-ray film.
The labels formed from either embossing a lead strip or assembling lead letters are placed directly on the envelope or cassette in which the X-ray film is placed, and an image is made in the film emulsion layer during the X-ray exposure portion of the X-ray procedure. The lead material absorbs X-ray radiation, blocking it from passing to the X-ray film, and leaves an unexposed image directly underneath. The unexposed area appears as a clear or lighter area in the X-ray film when the exposed film is developed. In this way, the label acts as a mask or stencil in creating an image in the film. Thus, in the first labeling method, the labeling process occurs during the exposure of the film to the X-ray radiation.
The labels made from embossing are created by a relatively sharp object, such as a ball point pen, or by an impact printer, such as a typewriter. On occasion, the embossing method using a relatively sharp object does not create a consistent mask or stencil from operator to operator. Thus, some labels might not produce a clear, legible image. The embossing method using a typewriter creates a more consistent label, but the necessity of using a lead strip and typewriter is inconvenient and time-consuming.
U.S. Pat. No. 4,764,948 to Hurwitz describes a method in which a substrate that is transparent to X-rays is coated first with a resilient layer also transparent to X-rays and then with an overlying thin layer of lead or tin foil that is opaque to X-rays. When the lead or tin foil layer is pressed upon by a pen or a typewriter key, the foil material in the pressed locations is selectively cut or fractured, allowing X-rays to pass through. If the label is placed upon the surface of an X-ray cassette or film envelope, it will serve as a stencil for selectively excluding the exposure of the underlying X-ray film except in the selected cut areas of the foil layer.
Labeling X-ray film using lead formed letters requires an inventory of various characters in assorted sizes, which must be attached to the X-ray film envelope or cassette. While the images created are consistent, collecting the various letters into the desired information, positioning them, and attaching them to the film can be a time consuming process, especially if such labels must be positioned and attached before making an exposure and then must be removed after each exposure.
U.S. Pat. No. 3,591,804 to Minasian and U.S. Pat. No. 3,590,244 to Kullman describe X-ray labeling systems that use pre-formed characters that block X-ray exposure. When the letters are placed over X-ray film, they shield the underlying film from X-ray exposure only in the area defined by the letters, creating an image in the emulsion layer of the film when the X-ray is taken.
The second major type of X-ray labeling method shields a small area of the X-ray film from X-ray exposure when the X-ray exposure is made and then utilizes visible light to expose the area using a mask that is imprinted with identifying data. X-ray film is more sensitive to visible light than standard photographic film. The small shielded area of the X-ray film, typically rectangular in shape, is first covered by a lead material, or lead blocker. When the film is exposed to X-ray radiation, the area under the lead blocker is shielded from the radiation and therefore is not exposed. Afterwards, white light, such as produced by a light bulb or camera flash, can be passed through a transparent identification mask or reflected off of an identification card onto the shielded area on the still-undeveloped X-ray film. The shielded area of the X-ray film is thereby exposed with the identification data, and the entire X-ray film can then be developed in the routine fashion, permanently identifying the X-ray image with the identification data. That is, the labeling process occurs after the film has been exposed to X-ray radiation.
The identification of the X-ray film after the initial X-ray exposure can be incorrect because of the time period between the initial exposure and development of the film. The identification data must be carefully positioned to be in the proper alignment with the shielded area. Further adding to the inconvenience is the fact that the identification data exposure using white light must be made in a darkened room. It is also impossible to determine whether the film has been exposed with the identification data prior to the development process, and therefore the film must be carefully tracked from initial exposure to development.
U.S. Pat. No. 4,679,222 to Knopp describes a system in which a lead shield is placed over a patient identification area and an X-ray exposure is made. The X-ray film and a translucent patient identification form are placed in a light exposure box and the form is carefully registered over the identification area. A light is then activated, shining through the translucent form and creating an image of the form in the film.
From the discussion above, it should be apparent that there is a need for an X-ray film identification system that can quickly and accurately label X-ray film with consistent identification data that is exposed into the X-ray film and can also be read under visible light. The present invention satisfies this need.